Water balance of the soil-plant system and water use efficiency by Eucalyptus species with different tolerances to water deficiency The growing concern with the use of water by crops and the search for greater water efficiency has been aggravated by the expansion of plantations in Brazil to marginal areas, with less water availability, which tends to increase with climate change. Knowledge about the morphological characteristics and the main physiological processes that control the growth of trees and water use is essential for the selection and improvement of drought-tolerant forest species. Thus, the present study aimed to: i) assess total and effective rainfall and monitor soil moisture variations; ii) estimate growth rates and characterize the crown structure of Eucalyptus and Corymbia species stands, which are: E. grandis (low-drought-tolerant), E. urophylla and E. cloeziana (moderatelydrought-tolerant), and E. brassiana, E. camaldulensis and C. citriodora (high-droughttolerant); and iii) calculate the water balance of the soil-plant system and evaluate the water use efficiency (WUE) for the production of wood in stands of E. grandis, E. urophylla and E. camaldulensis. The experiment was installed in March 2016 in the municipality of Itatinga-SP, Brazil. A useful subplot of 36 plants was installed to carry out non-destructive assessments on each species. The other lines of the plot were destined for destructive sampling. The species with the highest effective rainfall were E. brassiana and C. citriodora. Although E. grandis and E. urophylla, the most productive species, were the ones that had more water loss by interception, they were also the ones that presented the highest WUE for the synthesis of trunk biomass. E. grandis and E. camaldulensis were the species that transpired the most in 12 months (1112 mm and 797 mm, respectively). E. camaldulensis, although very tolerant to water deficit, proved to be an expensive species in the edaphoclimatic conditions of this site, which practically has no water restriction. This species consumed a lot of water and presented low WUE. E. urophylla, the species that transpired the least (638 mm), had a low impact on the water balance of the soil-plant system, and is also important in the carbon allocation process.

The first commercial thinning usually entails a high cost in harvest operations and a low resulting income. From a practical forestry perspective, a schematic spatial selection might be more efficient than a selective approach. Therefore, this study aimed to compare basal area, total and standing volumes, and periodic annual increment (PAI), as well as stand structure, between different thinning designs (selective and schematic thinning) and strategies (thinning once or more than once) over a long-term monitoring period of Scots pine (Pinus sylvestris) plantations in Sweden. We also evaluated the relevancy of distance-dependent competition indices (CIs) in individual tree growth models by comparing growth model predictions with the use of distance-dependent and distance-independent CIs. Despite higher heterogeneity in schematically thinned stands, there were no significant differences in standing and total volumes (m3·ha−1) among treatments in the short or long term. Although the inclusion of a distance-dependent CI improved the model slightly, distance-independent models predicted diameter growth just as effectively. Schematic thinning could be a viable option for a first commercial thinning or one-time thinning if, at least, one more thinning is included in the management plan, or if the motivating interest is mainly volume.